Cyclone separator

ABSTRACT

From the vortex chamber of a cyclone separator, a separated phase enters a discharge chamber coaxial with the vortex chamber and through which this phase flows toward a discharge opening while rotating around the axis of the chambers, thus following a screw-shaped track. Retarding means of the screw type are arranged coaxially in the discharge chamber and locked against rotation, the pitch of the retarding means being reversed relative to the pitch of the screw-shaped track of the separated phase.

United States Patent 1191 Frykhult 1 1 Feb. 13, 1973 [541 CYCLONE SEPARATOR 2,767,624 10/1956 Hoesch ..209 211 2,913,112 11/1959 Stavenger et a]. ..209/211 [75] g 3,105,044 9/1963 Troland ..210/512 We 4 3,513,642 5 1970 Comett ..209 144 73 Assignee; Aktiebolaget Ceueco, Tumbra 3,235,090 2/1966 Bose et al.... ..210/512 Sweden 3,372,532 3/1968 Campbell ..210/512 x 3,501,014 3/1970 Fitch et a1 ..209/211 X [22] Filed: March 18, 1970 Primary Examiner-Tim R. Miles [21 1 Appl' No" 20,539 Assistant ExaminerRalph J. Hill AttorneyDavis, Hoxie, Faithfull & Hapgood [30] Foreign Application Priority Data March 21, 1969 Sweden ..3959/69 [57] ABSTRACT From the vortex chamber of a cyclone separator, a [52] U.S.C| ..209/211, 210/512 separated phase enters a discharge chamber coaxial [51 II.- Cl ..B04c 5/14 ith the vgrtex chamber and through which this phase [58] Field of Search ..209/211, 144; 210/512 fl t w d a discharge opening while rotating around the axis of the chambers, thus following a References Cited screw-shaped track. Retarding means of the screw type are arranged coaxially in the discharge chamber UNITED STATES PATENTS and locked against rotation, the pitch of the retarding 2,236,548 4/1941 Prouty ..209/154 X means being reversed relative to the pitch of the 2,252,581 8/ 1941 Saint-Jacques ..209/144 screw-shaped track of the separated phase. 2,312,706 3/1943 Freeman ...209/211 2,375,826 5/1945 Scott ..209/211 3 Claims, 6 Drawing Figures PMENTEI] FEB I 3 I973 INVENTOR.

K H u LT RENE HELMER FRY CYCLONE SEPARATOR The present invention relates to cyclone separators of the type provided with a discharge chamber coaxialwith the separator and through which a phase that has been separated will flow in an axial direction toward a discharge opening, the separated phase also having a rotary movement around the axis of the discharge chamber and thus following a screw-shaped or spiral track.

Cyclone separators are utilized for various purposes. One of their major uses is in the cellulose industry for the purification of suspensions of cellulose fibers. Accordingly, conditions in the cellulose industry will be referred to as examples in the following description.

In a cellulose fiber suspension, impurities are present such as bark particles, metal particles, sand and the like, which must be separated from the suspension. They will otherwise cause stains on the paper made from the fiber suspension. When the suspension is treated in a cyclone separator, the impurities will form a heavy phase, which thus can be separated from the light phase containing the'cellulose fibers. It is obvious that the flow of the heavy phase should be controlled so that as small a portion as possible of the light phase will leave together with the heavy phase. Otherwise, losses will occur. On the other hand, the flow of the separated heavy phase must be controlled so that the discharged light phase will be purified to a satisfactory degree. Further, the need for very exact controlling of the cyclone separators in the cellulose industry has become extremely important lately, as it has been found necessary to prevent as far as possible the discharge of cellulose fibers into lakes and rivers, where they constitute an ill-natured water polluting agent.

Attempts have been made to control cyclone separators in various ways. It has been attempted, for example, to provide the discharge chamber with a radially directed discharge opening. It has also been attempted to arrange a throttling device at the discharge opening of the discharge chamber in order to create a suitable resistance against the flow of the heavy phase, this device being sometimes adjustable. The various solutions which have been attempted so far have not been satisfactory, however. Throttles provided in the discharge opening of the discharge chamber have a tendency to cause clogging of the discharge opening, as its free orifice is then too small.

Batteries of cyclone separators arranged in parallel are frequently used (so-called multiple cyclone separators). In such installations, it has been attempted to control the course of separation by controlling the rate of discharge from a receiving chamber for the separated heavy phase common to the cyclone separators arranged in parallel, thereby creating a counter pressure without throttling the discharge openings of the individual cyclone separators. These attempts have not been successful, however, without special arrangements. The reason for this is that the course of separation is so sensitive that the individual separators in a multiple cyclone separator provide different separation results, due to even small individual mechanical differences. It has therefore been necessary to calibrate carefully each individual separator in a multiple cyclone separator, in order to obtain a uniform separa-- tion result throughout the plant. This is obviously a drawback in connection with the previously known cyclone separators, causing expenses and difficulties.

One object of the present invention is to provide a discharge chamber for a cyclone separator which is so constructed as to enable decreasing the flow of the separated heavy phase to a desired minimum without resorting to throttling the discharge opening of the discharge chamber, thus avoiding clogging of the opening.

Another object is to provide a sufficiently great pressure drop in the discharge chamber of a cyclone separator without throttling its discharge opening, so that the separating function of the separator will not be dependent upon small inherent mechanical qualities. It will thus be possible to control effectively a multiple cyclone separator comprising a greatnumber of individual separators, by controlling the counter pressure in a receiving chamber common to the individual separators by means of one single valve in the discharge duct of the receiving chamber.

A still further object is to make it possible to provide the discharge chamber, without impairing the separation result, with a free discharge opening so large (even larger than the outlet of the vortex chamber) that no clogging can possibly occur.

According to the present invention, the discharge chamber of the cyclone separator contains means fixed therein and having a part located in the screw-shaped track or helical path of the separated phase for retarding its rotation as it passes toward the discharge opening of this chamber, the latter including a free space for flow of the separated phase from said fixed means to the discharge opening.

The invention will be more fully understood from the following description of a few embodiments of the same, with reference to the accompanying drawing, in which:

FIG. 1 is a side elevational view of a cyclone separator according to the invention, the lower part below the line III being in vertical section;

FIG. 2 is a view of the arrangement according to FIG. 1 as seen from above;

FIG. 3 is the vertical section below line III in FIG. 1 on an enlarged scale; and

FIGS. 4, 5 and 6 show further embodiments of the invention in vertical section.

In the drawing, reference numeral 1 designates a cyclone separator having a vortex chamber 2. The discharge chamber is indicated by reference numeral 3. The vortex chamber has at its upper end a tangential inlet 4 for the product to be treated, and an axial outlet 5 for the light phase separated in the vortex chamber. At its lower end, the cyclone separator discharges separated heavy phase into the discharge chamber 3 by an outlet 6. In the embodiments of the invention shown, the discharge chamber is provided with a discharge opening 7 for the separated heavy phase, this opening being coaxial with the outlet 6.

As is well known, a swiftly rotating vortex is developed in the vortex chamber 2, rotating in the direction shown by the arrow X in FIG. 2. By the action of the centrifugal force, the heavy phase is separated from the light phase and forms a layer adjacent to the wall of the vvortex chamber. The vortex has an axial movement downward, but near to the outlet 6 the light phase will develop an upwardly directed axial movement. In the center of the vortex, air or gases separated from the liquid will form a core around the axis of the vortex chamber.

The heavy phase layer originally formed adjacent to the wall of the vortex chamber 2 will continue to move in the downward direction while rotating around the axis of the discharge chamber 3. The heavy phase thus flows in an axial direction toward the discharge opening 7 of the discharge chamber, and at the same time it continues its rotary movement. The phase therefore flows along a screw-shaped or spiral track. When moving toward the discharge opening 7 of the discharge chamber according to the invention, the heavy phase impinges upon a member 12 (FIGS. 3 and 5), 12a (FIG. 4) or 12b (FIG. 6) arranged in the discharge chamber. This member in FIGS. 3, 4 and 5 is provided with a surface which, as seen in the direction of the rotation of the phase, has an inclination directed opposite to the inclination of the screw-shaped track of the phase. Thus, a force is created acting in a direction opposite to the direction of the axial movement of the heavy phase. In the embodiments shown in the drawing, this force is therefore directed upward and exerts a counter pressure against the pressure pushing the separated heavy phase in the downward direction toward the discharge opening 7 of the discharge chamber. A great pressure drop is thereby obtained in the discharge chamber. By suitably shaping the member 12, 12a, it is thus possible to obtain a counter pressure of a desired magnitude in each separate case, and a corresponding pressure drop without throttling the discharge opening 7 of the discharge chamber.

The effect obtained from the member 12 or 12a is best explained in the following way: It should be possible to create an axial counter pressure and a corresponding pressure drop without throttling the discharge opening of the discharge chamber, if a centrifugal pump with an open pump rotor, or a screwpump, were connected to the discharge opening 7 and arranged to tend to pump the discharged heavy phase in an axial direction opposite to the flow direction, and having a pressure lower than the pressure pushing the heavy phase toward the discharge opening. However, as the discharging phase in addition to the axial movement has a swift rotary movement as well, the same result could be obtained by arranging in the discharge chamber a fixed screw impeller, the pitch of which is reversed to that of the screw-shaped track of the discharging phase. The relative movement between the fixed impeller and the rotating phase then creates the desired counter pressure. In principle, therefore, the arrangement provides a non-rotary pumping means of the screw type in the discharge chamber 7 for retarding rotation of the rotating phase.

In the embodiment according to FIGS. 1 and 3, the retarding means is provided with a surface inclined in a direction reversed to that of the screw-shaped track of the discharging phase, and consists of a screw-shaped guide vane 12. It consists of a metal strip attached to the cylindrical wall of the discharge chamber by means of welding.

In the embodiment according to FIG. 4, the retarding means consists of two radially arranged vanes 12a, closely resembling propeller vanes. In this embodiment there is also a circular impact plate 8, previously known per se, which is coaxial with the outlet 6 of the cyclone separator. This impact plate acts as a check on the axial movement of the discharging phase and increases in combination with the vanes 12a their controlling function. The impact plate is supported by an upright 9.

There is a possibility that some particles of the separated heavy phase after having impinged against the retarding means 12 or 12a will rebound through the outlet 6 and mingle into the light phase discharging through the outlet 5. It is advantageous to prevent this by arranging a perforated partition between the impact plate 8 and the said retarding means. Such a partition 13 is shown in FIG. 5. It is provided with a circular opening 13a coaxial with the discharge chamber 3. In this embodiment, the diameter of the opening 13a is smaller than that of the impact plate 8. As a further precaution against heavy phase particles rebounding into the vortex chamber, the impact plate 8 may be provided with a cylindrical flange 14, which is coaxial with the impact plate and arranged on its side facing the discharge opening 7. This flange 14 then forms a labyrinth together with the partition 13, through which rebounding heavy phase particles can hardly pass.

In the embodiment according to FIG. 6 the said retarding means comprise those parts of a cylindrical bar 121) intersecting the axis of the discharge chamber, and perpendicular to the same, which are mainly situated in a plane with an inclination reversed to the pitch of the screw-shaped track of the separated phase. Also, when the rotating heavy phase impinges against the bar 12b, a pressure will arise which is directed upward. The bar 12b forms a part of a duct which by means of a vertical branch 9 supports the impact plate 8 which is in this case provided with a central bore 11. The air or gas core formed nearest and around the axis of the vortex chamber is sucked out through the channel thus formed.

The invention is not limited to the embodiments above described. Thus, the arrangement need not be orientated as shown in the drawing. Its main axis may, for instance, be horizontal. Also the arrangement as a whole may equally well be turned upside down. Further modifications are possible too. For instance, the partition 13 may consist of a plate provided with evenly distributed smaller orifices. The retarding means may, of course, be arranged some other way than the ways now suggested. It may even be arranged in a discharge duct leading the separated phase from the discharge chamber, in which case such duct is considered as an extension part of the discharge chamber. In the examples referred to, it has been implied that the treated material is a suspension in a liquid. The invention is equally applicable, however, to suspensions in air or in a gas. Further, in the examples referred to, reference has been made throughout to the discharge chamber being arranged at the outlet of the cyclone separator for separated heavy phase. To anybody skilled in the art, it is obvious that the invention can be equally well applied to the controlling of the light phase outlet, in which case the discharge chamber will, of course, be arranged at the light phase outlet. One discharge chamber may even be arranged at each one of the outlets 5 and 6.

Iclaim:

l. A cyclone separator forming a vortex chamber and a discharge chamber coaxial with the vortex chamber, said discharge chamber having at one end an inlet opening for receiving a separated phase from the vortex chamber and having at the opposite end a discharge opening, said vortex chamber having a tangential inlet for inducing rotation of a feed product in the separated phase from said fixed means to said discharge opening.

2. A cyclone separator according to claim 1, in which said discharge opening has a diameter larger than the diameter of the passage between the vortex chamber and said discharge chamber.

3. A cyclone separator according to claim 1, in which said discharge opening is coaxial with the discharge chamber. 

1. A cyclone separator forming a vortex chamber and a discharge chamber coaxial with the vortex chamber, said discharge chamber having at one end an inlet opening for receiving a separated phase from the vortex chamber and having at the opposite end a discharge opening, said vortex chamber having a tangential inlet for inducing rotation of a feed product in one direction around the axis of said chambers, whereby said separated phase rotates in said one direction in a helical path from said inlet opening to said discharge opening of the discharge chamber, said discharge opening being unrestricted, and means fixed in the discharge chamber for exerting a counter pressure therein, said fixed means having an inclined surface portion located in said helical path and oppositely inclined to the inclination of said helical path, said discharge chamber including a free space for flow of the separated phase from said fixed means to said discharge opening.
 1. A cyclone separator forming a vortex chamber and a discharge chamber coaxial with the vortex chamber, said discharge chamber having at one end an inlet opening for receiving a separated phase from the vortex chamber and having at the opposite end a discharge opening, said vortex chamber having a tangential inlet for inducing rotation of a feed product in one direction around the axis of said chambers, whereby said separated phase rotates in said one direction in a helical path from said inlet opening to said discharge opening of the discharge chamber, said discharge opening being unrestricted, and means fixed in the discharge chamber for exerting a counter pressure therein, said fixed means having an inclined surface portion located in said helical path and oppositely inclined to the inclination of said helical path, said discharge chamber including a free space for flow of the separated phase from said fixed means to said discharge opening.
 2. A cyclone separator according to claim 1, in which said discharge opening has a diameter larger than the diameter of the passage between the vortex chamber and said discharge chamber. 